A method for reducing axial force and pressure pulsation of a hydraulic turbine

Abstract

The invention discloses a method for reducing the axial force and pressure pulsation of a water turbine, belongs to the technical field of water turbines, and comprises the following steps: S1, a first high-pressure water flow channel is arranged on the top cover; S2, a second high-pressure water flow channel is arranged on the upper crown of the runner; S3, a third high-pressure water flow channel is arranged on the shaft end nut, and a drainage channel is arranged on the runner drainage cone; S4, high-pressure water is drained through the top cover, and the high-pressure water flows from the leak-proof ring into the first high-pressure water flow channel and the upper crown cavity, and then flows into the second high-pressure water flow channel through the first high-pressure water flow channel and the upper crown cavity, and then flows into the internal cavity above the runner body through the second high-pressure water flow channel, and then flows out from the internal cavity through the third high-pressure water flow channel and the drainage channel. The invention can significantly increase the leakage of gap leakage, avoid the accumulation of high-pressure water in the upper crown cavity, reduce the pressure in the upper crown cavity, thereby reducing the axial water thrust, effectively reducing the vortex belt strength and cavitation possibility, improving the unit performance, and improving the operation stability.

Description

Technical Field

[0001] The invention relates to the technical field of water turbines, and in particular to a method for reducing axial force and pressure pulsation of a water turbine. Background Art

[0002] The main function of the turbine top cover is to form a flow channel, withstand the corresponding water pressure, support and form the unit seal. If the water pressure in the upper crown cavity is too large, the top cover load will be too large, the upper crown axial water thrust will be too large, and the safe and stable operation of the unit will be affected. In order to reduce the leakage of the gap between the runner upper crown stop ring and the top cover stop ring, and reduce the leakage loss of the unit, the sealing structure gap between the traditional top cover structure and the runner upper crown is small, and a high-speed jet is easily formed in the sealing gap, which causes scouring and even damage to the top cover. In order to discharge high-pressure and high-speed water flow in time, reduce the water pressure between the upper crown and the upper cavity of the Francis turbine, and reduce the load of the thrust bearing and the vibration of the top cover, in the 1990s, the drainage of the Francis turbine top cover adopted a structural form of welding a pressure relief plate between the top cover and the runner, and discharged the leakage of the stop ring gap through the drain hole of the runner upper crown to reduce the water thrust of the runner. However, after running for too long, this structural form will cause the pressure relief plate to crack, causing the vibration of the unit.

[0003] With the rapid development of turbine design, in recent years, a structure has been added with a pressure relief pipe to quickly discharge the pressurized water to the tailwater without setting a pressure relief plate, which effectively reduces the axial load of the thrust bearing. However, as the operation time increases, cavitation wear occurs inside the pressure relief pipe, and the irregular flow of water in the pressure relief pipe generates noise.

[0004] The generation of spiral vortex belts under partial load conditions and spindle vortex belts under high load conditions are inherent characteristics of Francis turbines, which often lead to a significant increase in the pressure pulsation of the tailwater pipe of the unit under off-load operation, forming periodic impacts on the walls of the cone section and elbow section. The resulting tailwater pipe pressure pulsation is accompanied by low-frequency and high-amplitude characteristics, which is the main source of vibration and noise of the unit. The formation of the vortex belt starts at the end of the discharge cone. A relatively vacuum area will be formed in the center of the vortex belt near the runner outlet. When the pressure value drops to the vaporization pressure of the liquid temperature at this time, cavitation occurs in the vortex belt. When conducting a turbine model test, it is usually observed by eye whether the vortex belt has cavitation. Generally speaking, cavitation occurs when the vortex belt is visible to the naked eye. Studies have shown that cavity cavitation in the vortex belt will cause resonance with the water body, amplify the pressure pulsation of the tailwater pipe, and propagate upstream and downstream through the water body. If the pressure wave frequency is close to the natural frequency of the structural component, the resonance risk will be greatly increased. For this reason, many researchers have proposed measures to reduce the strength of the vortex belt in the tailwater pipe, such as changing the water flow motion state in the tailwater pipe, controlling the eccentricity of the vortex belt, introducing damping or improving the impeller design to reduce the circumferential component speed of the impeller outlet velocity under partial load conditions.

[0005] At present, in previous mixed flow turbine model tests, the main method used is to arrange pressure reducing pipes or balancing pipes to discharge gap leakage. However, this method will increase the axial water thrust and reduce the operating efficiency of the unit. At the same time, there is also a lack of a method that fully utilizes the unit structure to more conveniently and efficiently suppress the vortex belt strength and reduce the pressure pulsation of the tailwater pipe.

[0006] A Chinese patent document with publication number CN114215676 A and publication date March 22, 2022 discloses a method for reducing the pressure pulsation of a turbine tail water, characterized in that it includes the following steps: a. The tail water coming out of the turbine runner blades passes through a vortex suppression device in the straight cone section of the turbine tail water pipe, thereby reducing the tail water pressure pulsation; the structure of the vortex suppression device is as follows: an intermediate shaft is arranged in the turbine tail water pipe, and a spiral guide plate is arranged outside the intermediate shaft, and the spiral radius of the spiral guide plate increases from top to bottom; b. At the same time, the tail water coming out of the turbine runner blades is replenished with air through the straight cone section of the turbine tail water pipe to adjust the pressure in the center of the tail water vortex belt, and the structure of the air replenishment device is as follows: the intermediate shaft is a hollow shaft, and the air replenishment pipe passes through the tail water pipe wall and is connected with the hollow shaft, and an air replenishment hole inclined downward is arranged on the hollow shaft to replenish the tail water pipe with air.

[0007] The method for reducing the pressure pulsation of the tail water of a hydraulic turbine disclosed in the patent document can reduce the pressure pulsation of the tail water of a hydraulic turbine by setting an air supply and vortex suppression device. However, there is still the problem that high-pressure water is easy to accumulate in the upper crown cavity, which increases the pressure in the upper crown cavity and affects the operating stability of the unit. Summary of the invention

[0008] In order to overcome the defects of the above-mentioned prior art, the present invention provides a method for reducing the axial force and pressure pulsation of a turbine. The present invention can significantly increase the leakage rate of gap leakage, avoid the accumulation of high-pressure water in the upper crown cavity, reduce the pressure in the upper crown cavity, thereby reducing the axial water thrust, effectively reducing the vortex belt strength and the possibility of cavitation, improving the performance of the unit, and improving the operating stability.

[0009] The present invention is achieved through the following technical solutions:

[0010] A method for reducing axial force and pressure pulsation of a water turbine, characterized by comprising the following steps:

[0011] S1. A first high-pressure water flow channel is provided on the top cover, and the first high-pressure water flow channel is connected with the upper crown cavity of the runner;

[0012] S2. A second high-pressure water flow channel is provided on the upper crown of the runner, and the internal cavity formed by the upper crown of the runner and the runner body is connected with the cavity of the upper crown through the second high-pressure water flow channel;

[0013] S3, a third high-pressure water flow channel is provided on the shaft end nut, a drainage channel is provided on the runner drainage cone, and the third high-pressure water flow channel is connected with the drainage channel;

[0014] S4. High-pressure water is discharged through the top cover. The high-pressure water flows from the leak-proof ring into the first high-pressure water flow channel and the upper crown cavity, and then flows into the second high-pressure water flow channel through the first high-pressure water flow channel and the upper crown cavity, and then flows into the internal cavity above the impeller body through the second high-pressure water flow channel, and then flows out from the internal cavity through the third high-pressure water flow channel and the drain channel.

[0015] In S1, the upper crown cavity refers to the cavity formed by the top cover and the upper crown of the rotating wheel.

[0016] In S1, the first high-pressure water flow channel includes an inclined hole on the top cover, a transverse hole on the top cover and a vertical hole, and the inclined hole on the top cover, the transverse hole on the top cover and the vertical hole are connected.

[0017] The top cover inclined hole connects the upper crown cavity of the rotating wheel with the top cover transverse hole.

[0018] The vertical hole connects the top cover transverse hole and the upper crown cavity of the rotating wheel.

[0019] In S2, the second high-pressure water flow channel is an upper crown inclined hole, and the internal cavity formed by the upper crown of the runner and the runner body is connected to the upper crown cavity through the upper crown inclined hole.

[0020] In S3, the third high-pressure water flow channel is a screw hole, and the screw hole is connected to the water drain channel.

[0021] In S3, the drainage channel includes a drainage cone hole and a drainage cone inclined hole.

[0022] The screw hole on the shaft end nut is communicated with the drain cone hole on the runner drain cone.

[0023] The screw hole comprises a transverse hole and a longitudinal hole, and the transverse hole and the longitudinal hole are connected.

[0024] The inclined hole of the drainage cone is located above the drainage cone hole.

[0025] The drainage cone hole comprises a first drainage hole and a second drainage hole, the first drainage hole is located above the second drainage hole, and the first drainage hole and the second drainage hole are connected.

[0026] The aperture of the first drain hole is the same as the aperture of the longitudinal hole of the screw hole.

[0027] The aperture of the second drainage hole is larger than the aperture of the first drainage hole.

[0028] In S4, the high-pressure water is drained through the top cover, which specifically means that the high-pressure water flows from the leak-proof ring through the inclined hole of the top cover into the horizontal hole of the top cover and the upper crown cavity, then flows into the vertical hole through the horizontal hole of the top cover and the upper crown cavity, flows into the inclined hole of the upper crown through the vertical hole, and then flows into the internal cavity above the impeller body through the inclined hole of the upper crown, and then flows out from the internal cavity through the screw hole of the shaft end nut, the drainage cone hole and the drainage cone inclined hole.

[0029] The beneficial effects of the present invention are mainly manifested in the following aspects:

[0030] 1. Compared with the prior art, the present invention can significantly increase the leakage rate of gap leakage, avoid the accumulation of high-pressure water in the upper crown cavity, reduce the pressure in the upper crown cavity, thereby reducing the axial water thrust, effectively reducing the vortex belt strength and cavitation possibility, improving the unit performance, and improving the operation stability.

[0031] 2. In the present invention, high-pressure water flows from the leak-proof ring into the first high-pressure water flow channel and the upper crown cavity, then flows into the second high-pressure water flow channel through the first high-pressure water flow channel and the upper crown cavity, then flows into the internal cavity above the impeller body through the second high-pressure water flow channel, and then flows out from the internal cavity through the third high-pressure water flow channel and the drain channel. Compared with the prior art that uses a balancing pipe hole in the top cover, gap leakage at the leak-proof ring can pass through the first high-pressure water flow channel and the upper crown cavity at the same time, which can buffer the high-speed water flow formed by the gap seal, reduce the flow rate of the high-speed jet, stabilize the flow state inside the top cover, and accelerate the gap leakage to flow out toward the impeller outlet, thereby reducing the water pressure between the top cover and the impeller upper crown and reducing the axial water thrust of the unit.

[0032] 3. In the present invention, the design principle of the entire high-pressure water discharge through the top cover is simple and easy to implement, and can effectively reduce the axial water thrust of the turbine and the pressure pulsation of the tailwater pipe, and has good applicability.

[0033] 4. In the present invention, the drainage channel includes a drainage cone hole and a drainage cone inclined hole. The screw hole on the shaft end nut is connected with the drainage cone hole on the runner drainage cone, which can effectively ensure that the runner drainage cone has sufficient drainage flow and water flow energy to destroy the low-pressure environment formed by the vortex belt appearing under partial load operating conditions, thereby effectively solving the unsteady flow problem inside the turbine, especially the pressure pulsation problem caused by the vortex belt in the tailwater pipe.

[0034] 5. In the present invention, high-pressure water is discharged through the top cover, which specifically means that the high-pressure water flows from the leak-proof ring through the inclined hole of the top cover into the horizontal hole of the top cover and the upper crown cavity, then flows into the vertical hole through the horizontal hole of the top cover and the upper crown cavity, flows into the inclined hole of the upper crown through the vertical hole, then flows into the internal cavity above the impeller body through the inclined hole of the upper crown, and then flows out from the internal cavity through the screw hole of the shaft end nut and the drain cone hole in sequence, which can reduce the scouring effect of the high-speed jet of high-pressure water on the top cover, destroy the low-pressure environment of the tail water vortex, effectively reduce the strength of the vortex and the possibility of cavitation, thereby reducing the pressure pulsation caused by the tail water vortex, and effectively improving the operating stability of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0036] Figure 1 This is a schematic diagram of high-pressure water drainage of the present invention;

[0037] Figure 2 It is a schematic structural diagram of the rotating wheel of the present invention;

[0038] Markings in the figure: 1. top cover, 2. first high-pressure water flow channel, 3. runner blades, 4. upper crown cavity, 5. runner upper crown, 6. second high-pressure water flow channel, 7. runner body, 8. internal cavity, 9. shaft end nut, 10. main shaft, 11. third high-pressure water flow channel, 12. runner drain cone, 13. drain channel, 14. leak-proof ring, 15. top cover inclined hole, 16. top cover horizontal hole, 17. vertical hole, 18. upper crown inclined hole, 19. screw hole, 20. drain cone hole, 21. drain cone inclined hole, 22. runner lower ring, 23. horizontal hole, 24. longitudinal hole, 25. first drain hole, 26. second drain hole. DETAILED DESCRIPTION

[0039] Example 1

[0040] See also Figure 1 and Figure 2 , a method for reducing the axial force and pressure pulsation of a turbine, comprising the following steps:

[0041] S1. A first high-pressure water flow channel 2 is provided on the top cover 1, and the first high-pressure water flow channel 2 is connected to the upper crown cavity 4 of the runner;

[0042] S2. A second high-pressure water flow channel 6 is provided on the runner upper crown 5. The internal cavity 8 formed by the runner upper crown 5 and the runner body 7 is connected with the upper crown cavity 4 through the second high-pressure water flow channel 6;

[0043] S3, a third high-pressure water flow channel 11 is provided on the shaft end nut 9, a drain channel 13 is provided on the runner drain cone 12, and the third high-pressure water flow channel 11 is connected to the drain channel 13;

[0044] S4, high-pressure water is discharged through the top cover 1, and the high-pressure water flows from the leak-proof ring 14 into the first high-pressure water flow channel 2 and the upper crown cavity 4, and then flows into the second high-pressure water flow channel 6 through the first high-pressure water flow channel 2 and the upper crown cavity 4, and then flows into the internal cavity 8 above the impeller body 7 through the second high-pressure water flow channel 6, and then flows out from the internal cavity 8 through the third high-pressure water flow channel 11 and the drain channel 13.

[0045] This embodiment is the most basic implementation method. Compared with the prior art, the present invention can significantly increase the leakage rate of gap leakage, avoid the accumulation of high-pressure water in the upper crown cavity 4, reduce the pressure in the upper crown cavity 4, thereby reducing the axial water thrust, effectively reducing the vortex belt strength and cavitation possibility, improving the unit performance, and improving the operation stability.

[0046] Example 2

[0047] See also Figure 1 and Figure 2 , a method for reducing the axial force and pressure pulsation of a turbine, comprising the following steps:

[0048] S1. A first high-pressure water flow channel 2 is provided on the top cover 1, and the first high-pressure water flow channel 2 is connected to the upper crown cavity 4 of the runner;

[0049] S2. A second high-pressure water flow channel 6 is provided on the runner upper crown 5. The internal cavity 8 formed by the runner upper crown 5 and the runner body 7 is connected with the upper crown cavity 4 through the second high-pressure water flow channel 6;

[0050] S3, a third high-pressure water flow channel 11 is provided on the shaft end nut 9, a drain channel 13 is provided on the runner drain cone 12, and the third high-pressure water flow channel 11 is connected to the drain channel 13;

[0051] S4, high-pressure water is discharged through the top cover 1, and the high-pressure water flows from the leak-proof ring 14 into the first high-pressure water flow channel 2 and the upper crown cavity 4, and then flows into the second high-pressure water flow channel 6 through the first high-pressure water flow channel 2 and the upper crown cavity 4, and then flows into the internal cavity 8 above the impeller body 7 through the second high-pressure water flow channel 6, and then flows out from the internal cavity 8 through the third high-pressure water flow channel 11 and the drain channel 13.

[0052] Preferably, in S1, the upper crown cavity 4 refers to the cavity formed by the top cover 1 and the upper crown 5 of the rotating wheel.

[0053] In the above S1, the first high-pressure water flow channel 2 includes a top cover inclined hole 15, a top cover transverse hole 16 and a vertical hole 17, and the top cover inclined hole 15, the top cover transverse hole 16 and the vertical hole 17 are connected.

[0054] The top cover inclined hole 15 connects the upper crown cavity 4 of the rotating wheel with the top cover transverse hole 16 .

[0055] The vertical hole 17 connects the top cover transverse hole 16 and the upper crown cavity 4 of the rotating wheel.

[0056] This embodiment is a preferred implementation method. High-pressure water flows from the leak-proof ring 14 into the first high-pressure water flow channel 2 and the upper crown cavity 4, then flows into the second high-pressure water flow channel 6 through the first high-pressure water flow channel 2 and the upper crown cavity 4, then flows into the internal cavity 8 above the impeller body 7 through the second high-pressure water flow channel 6, and then flows out from the internal cavity 8 through the third high-pressure water flow channel 11 and the drain channel 13. Compared with the prior art that uses a balancing pipe hole in the top cover 1, the gap leakage at the leak-proof ring 14 can pass through the first high-pressure water flow channel 2 and the upper crown cavity 4 at the same time, which can buffer the high-speed water flow formed by the gap seal, reduce the flow rate of the high-speed jet, stabilize the internal flow state of the top cover 1, and accelerate the gap leakage to flow out toward the impeller outlet, thereby reducing the water pressure between the top cover 1 and the impeller upper crown 5 and reducing the axial water thrust of the unit.

[0057] Example 3

[0058] See also Figure 1 and Figure 2 , a method for reducing the axial force and pressure pulsation of a turbine, comprising the following steps:

[0059] S1. A first high-pressure water flow channel 2 is provided on the top cover 1, and the first high-pressure water flow channel 2 is connected to the upper crown cavity 4 of the runner;

[0060] S2. A second high-pressure water flow channel 6 is provided on the runner upper crown 5. The internal cavity 8 formed by the runner upper crown 5 and the runner body 7 is connected with the upper crown cavity 4 through the second high-pressure water flow channel 6;

[0061] S3, a third high-pressure water flow channel 11 is provided on the shaft end nut 9, a drain channel 13 is provided on the runner drain cone 12, and the third high-pressure water flow channel 11 is connected to the drain channel 13;

[0062] S4, high-pressure water is discharged through the top cover 1, and the high-pressure water flows from the leak-proof ring 14 into the first high-pressure water flow channel 2 and the upper crown cavity 4, and then flows into the second high-pressure water flow channel 6 through the first high-pressure water flow channel 2 and the upper crown cavity 4, and then flows into the internal cavity 8 above the impeller body 7 through the second high-pressure water flow channel 6, and then flows out from the internal cavity 8 through the third high-pressure water flow channel 11 and the drain channel 13.

[0063] In S1, the upper crown cavity 4 refers to the cavity formed by the top cover 1 and the upper crown 5 of the rotating wheel.

[0064] In the above S1, the first high-pressure water flow channel 2 includes a top cover inclined hole 15, a top cover transverse hole 16 and a vertical hole 17, and the top cover inclined hole 15, the top cover transverse hole 16 and the vertical hole 17 are connected.

[0065] The top cover inclined hole 15 connects the upper crown cavity 4 of the rotating wheel with the top cover transverse hole 16 .

[0066] The vertical hole 17 connects the top cover transverse hole 16 and the upper crown cavity 4 of the rotating wheel.

[0067] In S2 , the second high-pressure water flow channel 6 is an upper crown inclined hole 18 , and the internal cavity 8 formed by the runner upper crown 5 and the runner body 7 is connected to the upper crown cavity 4 through the upper crown inclined hole 18 .

[0068] In S3 , the third high-pressure water flow channel 11 is a screw hole 19 , and the screw hole 19 is connected to the water discharge channel 13 .

[0069] In S3 , the drainage channel 13 includes a drainage cone hole 20 and a drainage cone inclined hole 21 .

[0070] This embodiment is another preferred implementation method. The design principle of discharging the entire high-pressure water through the top cover 1 is simple and easy to implement. It can effectively reduce the axial water thrust of the turbine and the pressure pulsation of the tailwater pipe and has good applicability.

[0071] Example 4

[0072] See also Figure 1 and Figure 2 , a method for reducing the axial force and pressure pulsation of a turbine, comprising the following steps:

[0073] S1. A first high-pressure water flow channel 2 is provided on the top cover 1, and the first high-pressure water flow channel 2 is connected to the upper crown cavity 4 of the runner;

[0074] S2. A second high-pressure water flow channel 6 is provided on the runner upper crown 5. The internal cavity 8 formed by the runner upper crown 5 and the runner body 7 is connected with the upper crown cavity 4 through the second high-pressure water flow channel 6;

[0075] S3, a third high-pressure water flow channel 11 is provided on the shaft end nut 9, a drain channel 13 is provided on the runner drain cone 12, and the third high-pressure water flow channel 11 is connected to the drain channel 13;

[0076] S4, high-pressure water is discharged through the top cover 1, and the high-pressure water flows from the leak-proof ring 14 into the first high-pressure water flow channel 2 and the upper crown cavity 4, and then flows into the second high-pressure water flow channel 6 through the first high-pressure water flow channel 2 and the upper crown cavity 4, and then flows into the internal cavity 8 above the impeller body 7 through the second high-pressure water flow channel 6, and then flows out from the internal cavity 8 through the third high-pressure water flow channel 11 and the drain channel 13.

[0077] In S1, the upper crown cavity 4 refers to the cavity formed by the top cover 1 and the upper crown 5 of the rotating wheel.

[0078] In the above S1, the first high-pressure water flow channel 2 includes a top cover inclined hole 15, a top cover transverse hole 16 and a vertical hole 17, and the top cover inclined hole 15, the top cover transverse hole 16 and the vertical hole 17 are connected.

[0079] The top cover inclined hole 15 connects the upper crown cavity 4 of the rotating wheel with the top cover transverse hole 16 .

[0080] The vertical hole 17 connects the top cover transverse hole 16 and the upper crown cavity 4 of the rotating wheel.

[0081] In S2 , the second high-pressure water flow channel 6 is an upper crown inclined hole 18 , and the internal cavity 8 formed by the runner upper crown 5 and the runner body 7 is connected to the upper crown cavity 4 through the upper crown inclined hole 18 .

[0082] Further preferably, in S3 , the third high-pressure water flow channel 11 is a screw hole 19 , and the screw hole 19 is connected to the water drain channel 13 .

[0083] In S3 , the drainage channel 13 includes a drainage cone hole 20 and a drainage cone inclined hole 21 .

[0084] The screw hole 19 on the shaft end nut 9 is communicated with the drain cone hole 20 on the runner drain cone 12 .

[0085] The screw hole 19 includes a transverse hole 23 and a longitudinal hole 24 , and the transverse hole 23 and the longitudinal hole 24 are connected.

[0086] The drain cone inclined hole 21 is located above the drain cone hole 20 .

[0087] The drainage cone hole 20 includes a first drainage hole 25 and a second drainage hole 26 . The first drainage hole 25 is located above the second drainage hole 26 , and the first drainage hole 25 and the second drainage hole 26 are connected.

[0088] The diameter of the first drain hole 25 is the same as the diameter of the longitudinal hole 24 of the screw hole 19 .

[0089] The diameter of the second drainage hole 26 is larger than the diameter of the first drainage hole 25 .

[0090] This embodiment is another preferred implementation mode. The drainage channel 13 includes a drainage cone hole 20 and a drainage cone inclined hole 21. The screw hole 19 on the shaft end nut 9 is connected to the drainage cone hole 20 on the runner drainage cone 12, which can effectively ensure that the runner drainage cone 12 has sufficient drainage flow and water flow energy to destroy the low-pressure environment formed by the vortex belt appearing under partial load operating conditions, thereby effectively solving the unsteady flow problem inside the turbine, especially the pressure pulsation problem caused by the vortex belt in the tail water pipe.

[0091] Example 5

[0092] See also Figure 1 and Figure 2 , a method for reducing the axial force and pressure pulsation of a turbine, comprising the following steps:

[0093] S1. A first high-pressure water flow channel 2 is provided on the top cover 1, and the first high-pressure water flow channel 2 is connected to the upper crown cavity 4 of the runner;

[0094] S2. A second high-pressure water flow channel 6 is provided on the runner upper crown 5. The internal cavity 8 formed by the runner upper crown 5 and the runner body 7 is connected with the upper crown cavity 4 through the second high-pressure water flow channel 6;

[0095] S3, a third high-pressure water flow channel 11 is provided on the shaft end nut 9, a drain channel 13 is provided on the runner drain cone 12, and the third high-pressure water flow channel 11 is connected to the drain channel 13;

[0096] S4, high-pressure water is discharged through the top cover 1, and the high-pressure water flows from the leak-proof ring 14 into the first high-pressure water flow channel 2 and the upper crown cavity 4, and then flows into the second high-pressure water flow channel 6 through the first high-pressure water flow channel 2 and the upper crown cavity 4, and then flows into the internal cavity 8 above the impeller body 7 through the second high-pressure water flow channel 6, and then flows out from the internal cavity 8 through the third high-pressure water flow channel 11 and the drain channel 13.

[0097] In S1, the upper crown cavity 4 refers to the cavity formed by the top cover 1 and the upper crown 5 of the rotating wheel.

[0098] In the above S1, the first high-pressure water flow channel 2 includes a top cover inclined hole 15, a top cover transverse hole 16 and a vertical hole 17, and the top cover inclined hole 15, the top cover transverse hole 16 and the vertical hole 17 are connected.

[0099] The top cover inclined hole 15 connects the upper crown cavity 4 of the rotating wheel with the top cover transverse hole 16 .

[0100] The vertical hole 17 connects the top cover transverse hole 16 and the upper crown cavity 4 of the rotating wheel.

[0101] In S2 , the second high-pressure water flow channel 6 is an upper crown inclined hole 18 , and the internal cavity 8 formed by the runner upper crown 5 and the runner body 7 is connected to the upper crown cavity 4 through the upper crown inclined hole 18 .

[0102] In S3 , the third high-pressure water flow channel 11 is a screw hole 19 , and the screw hole 19 is connected to the water discharge channel 13 .

[0103] In S3 , the drainage channel 13 includes a drainage cone hole 20 and a drainage cone inclined hole 21 .

[0104] The screw hole 19 on the shaft end nut 9 is communicated with the drain cone hole 20 on the runner drain cone 12 .

[0105] The screw hole 19 includes a transverse hole 23 and a longitudinal hole 24 , and the transverse hole 23 and the longitudinal hole 24 are connected.

[0106] The drain cone inclined hole 21 is located above the drain cone hole 20 .

[0107] More preferably, the drainage cone hole 20 includes a first drainage hole 25 and a second drainage hole 26 , the first drainage hole 25 is located above the second drainage hole 26 , and the first drainage hole 25 and the second drainage hole 26 are connected.

[0108] The diameter of the first drain hole 25 is the same as the diameter of the longitudinal hole 24 of the screw hole 19 .

[0109] The diameter of the second drainage hole 26 is larger than the diameter of the first drainage hole 25 .

[0110] In the above S4, the high-pressure water is drained through the top cover 1, which specifically means that the high-pressure water flows from the leak-proof ring 14 through the top cover inclined hole 15 into the top cover horizontal hole 16 and the upper crown cavity 4, and then flows into the vertical hole 17 through the top cover horizontal hole 16 and the upper crown cavity 4, and then flows into the upper crown inclined hole 18 through the vertical hole 17, and then flows into the internal cavity 8 above the impeller body 7 through the upper crown inclined hole 18, and then flows out from the internal cavity 8 through the screw hole 19 of the shaft end nut 9, the drainage cone hole 20 and the drainage cone inclined hole 21.

[0111] This embodiment is the best implementation mode. The high-pressure water is discharged through the top cover 1, which specifically means that the high-pressure water flows from the leak-proof ring 14 through the top cover inclined hole 15 into the top cover horizontal hole 16 and the upper crown cavity 4, and then flows into the vertical hole 17 through the top cover horizontal hole 16 and the upper crown cavity 4, and then flows into the upper crown inclined hole 18 through the vertical hole 17, and then flows into the internal cavity 8 above the impeller body 7 through the upper crown inclined hole 18, and then flows out from the internal cavity 8 through the screw hole 19 of the shaft end nut 9 and the drain cone hole 20 in turn, which can reduce the scouring effect of the high-speed jet of high-pressure water on the top cover 1, destroy the low-pressure environment of the tail water vortex, effectively reduce the strength of the vortex and the possibility of cavitation, thereby reducing the pressure pulsation caused by the tail water vortex, and effectively improving the operating stability of the unit.

[0112] The basic principles of the present invention are as follows:

[0113] Since the balance pipe technical solution adopted in the prior art cannot timely remove the high-pressure water flow in the upper crown cavity 4, the drainage volume is affected by the pressure difference and the pipe diameter, and the drainage flow to the downstream tail water is insufficient, causing the high-pressure and high-speed water flow entering from the leak-proof ring 14 to be retained for too long in the narrow upper crown cavity 4 formed by the top cover 1 and the runner upper crown 5, thereby causing the axial water thrust of the turbine to be too large. The present invention comprehensively considers the unit structure form, and without significantly changing the unit structural components, the multi-hole combined drainage solution adopted by the present invention widens the flow range of high-pressure water through the first high-pressure water flow channel 2, the second high-pressure water flow channel 6, the third high-pressure water flow channel 11 and the drainage channel 13, significantly increases the drainage flow, and timely discharges the high-pressure and high-speed water flow entering from the leak-proof ring 14, thereby effectively reducing the axial water thrust of the turbine.

[0114] Due to the influence of the strength of the vortex belt inside the tailwater pipe, a relative vacuum area will appear in the flow field inside the tailwater pipe, resulting in large pressure pulsation, posing a threat to the safe and stable operation of the unit. With the present invention, by virtue of the pressure difference between the low-pressure and high-pressure water flows at the vortex belt, the high-pressure and high-speed water flow can be further discharged downstream from the drainage channel 13 formed by the drainage cone hole 20 and the drainage cone inclined hole 21, thereby impacting the vortex belt of the tailwater pipe, increasing the pressure at the center of the vortex belt, and reducing the strength level of the cavitation vortex belt, thereby effectively reducing the pressure pulsation of the tailwater pipe.

[0115] The following is a calculation comparison of the unit axial water thrust and the tailwater pipe pressure pulsation when the drainage structure of the present invention is used and the prior art is used to set the balance pipe hole drainage on the top cover, see Table 1:

[0116] Table 1

[0117]

[0118] Among them, the unit axial water thrust Calculated by formula 1;

[0119] Formula 1

[0120] Where: F ED is the unit axial water thrust, F a is the turbine axial water thrust, H To test the water head, D is the nominal diameter of the runner, ρ is the water density, g is the acceleration due to gravity.

[0121] The time-domain amplitude of the pressure pulsation is calculated based on the maximum peak-to-peak value of the pressure pulsation within the time-domain range, that is, a mixed frequency double peak value calculation with a 97% confidence level is performed on the pressure pulsation time-domain waveform diagram recorded in the test.

[0122] The relative value of the mixed frequency of the tailwater tube cone pressure pulsation, that is, the tailwater tube pressure pulsation is calculated by formula 2;

[0123] Formula 2

[0124] Where: A is the relative value of the mixed frequency of the tailwater cone pressure pulsation, ΔH is the double amplitude of pressure pulsation, H To test the water head.

[0125] It can be seen from Table 1 that the method of the present invention can effectively reduce the axial water thrust of the turbine and the pressure pulsation of the tailwater pipe.

Claims

1. A method for reducing axial force and pressure pulsation of a turbine, characterized in that: The following steps are involved: S1. A first high-pressure water flow channel (2) is provided on the top cover (1), wherein the first high-pressure water flow channel (2) is connected to the upper crown cavity (4) of the runner; S2. A second high-pressure water flow channel (6) is provided on the upper crown (5) of the runner, and an internal cavity (8) formed by the upper crown (5) of the runner and the runner body (7) is connected to the upper crown cavity (4) through the second high-pressure water flow channel (6); S3, a third high-pressure water flow channel (11) is provided on the shaft end nut (9), a water discharge channel (13) is provided on the runner water discharge cone (12), and the third high-pressure water flow channel (11) is in communication with the water discharge channel (13); S4, high-pressure water is discharged through the top cover (1), and the high-pressure water flows from the leak-proof ring (14) into the first high-pressure water flow channel (2) and the upper crown cavity (4), and then flows through the first high-pressure water flow channel (2) and the upper crown cavity (4) into the second high-pressure water flow channel (6), and then flows through the second high-pressure water flow channel (6) into the internal cavity (8) above the rotor body (7), and then flows out of the internal cavity (8) through the third high-pressure water flow channel (11) and the drain channel (13); In S1, the first high-pressure water flow channel (2) comprises a top cover inclined hole (15), a top cover transverse hole (16) and a vertical hole (17), and the top cover inclined hole (15), the top cover transverse hole (16) and the vertical hole (17) are connected; In the above-mentioned S2, the second high-pressure water flow channel (6) is an upper crown inclined hole (18), and the internal cavity (8) formed by the upper crown (5) of the runner and the runner body (7) is connected to the upper crown cavity (4) through the upper crown inclined hole (18).

2. A method for reducing axial force and pressure pulsation of a water turbine according to claim 1, characterized in that: In S1, the upper crown cavity (4) refers to the cavity formed by the top cover (1) and the upper crown (5) of the rotating wheel.

3. A method for reducing axial force and pressure pulsation of a water turbine according to claim 1, characterized in that: The top cover inclined hole (15) connects the upper crown cavity (4) of the rotating wheel and the top cover transverse hole (16).

4. A method for reducing axial force and pressure pulsation of a water turbine according to claim 3, characterized in that: The vertical hole (17) connects the top cover transverse hole (16) and the upper crown cavity (4) of the rotating wheel.

5. The method for reducing the axial force and pressure pulsation of a water turbine according to claim 1, characterized in that: In S3, the third high-pressure water flow channel (11) is a screw hole (19), and the screw hole (19) is connected to the water discharge channel (13).

6. A method for reducing axial force and pressure pulsation of a water turbine according to claim 5, characterized in that: In S3, the water discharge channel (13) comprises a water discharge cone hole (20) and a water discharge cone inclined hole (21).

7. A method for reducing axial force and pressure pulsation of a water turbine according to claim 6, characterized in that: The screw hole (19) on the shaft end nut (9) is in communication with the drain cone hole (20) on the runner drain cone (12).

8. The method for reducing the axial force and pressure pulsation of a water turbine according to claim 6, characterized in that: The screw hole (19) comprises a transverse hole (23) and a longitudinal hole (24), and the transverse hole (23) and the longitudinal hole (24) are connected.

9. A method for reducing axial force and pressure pulsation of a water turbine according to claim 6, characterized in that: The drain cone inclined hole (21) is located above the drain cone hole (20).

10. A method for reducing axial force and pressure pulsation of a water turbine according to claim 8, characterized in that: The drainage cone hole (20) comprises a first drainage hole (25) and a second drainage hole (26); the first drainage hole (25) is located above the second drainage hole (26); and the first drainage hole (25) and the second drainage hole (26) are connected.

11. A method for reducing axial force and pressure pulsation of a water turbine according to claim 10, characterized in that: The diameter of the first drain hole (25) is the same as the diameter of the longitudinal hole (24) of the screw hole (19).

12. A method for reducing axial force and pressure pulsation of a water turbine according to claim 10, characterized in that: The diameter of the second drainage hole (26) is greater than the diameter of the first drainage hole (25).

13. A method for reducing axial force and pressure pulsation of a water turbine according to claim 6, characterized in that: In the above-mentioned S4, the high-pressure water is discharged through the top cover (1) and specifically refers to the high-pressure water flowing from the leak-proof ring (14) through the top cover inclined hole (15) into the top cover horizontal hole (16) and the upper crown cavity (4), then flowing into the vertical hole (17) through the top cover horizontal hole (16) and the upper crown cavity (4), flowing into the upper crown inclined hole (18) through the vertical hole (17), and then flowing into the internal cavity (8) above the rotor body (7) through the upper crown inclined hole (18), and then flowing out from the internal cavity (8) through the screw hole (19) of the shaft end nut (9), the drain cone hole (20) and the drain cone inclined hole (21).

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